More than thirty years ago, many household laundry detergents were made of branched alkylbenzene sulfonates (BABS). BABS are manufactured from branched alkylbenzenes (BAB). Then, it became apparent that household laundry detergents made of BABS were gradually polluting rivers and lakes. Investigation into the problem led to the recognition that BABS were slow to biodegrade. Solution of the problem led to the manufacture of detergents made of linear alkylbenzene sulfonates (LABS), which were found to biodegrade more rapidly than BABS. Today, detergents made of LABS are manufactured worldwide.
LABS are manufactured from linear alkylbenzenes (LAB). The standard process used by the petrochemical industry for producing LAB consists of dehydrogenating linear paraffins to linear olefins and then alkylating benzene with the linear olefins in the presence of a catalyst such as HF or a solid catalyst. LAB are phenyl-alkanes comprising a linear aliphatic alkyl group and a phenyl group and have the general formula n-phenyl-alkane. In LAB produced using HF catalyst the phenyl group is slightly more likely to attach to a secondary carbon near the center as opposed to near the end of the linear aliphatic alkyl group, and typically only about 18 wt.-% of the n-phenyl-alkanes are 2-phenyl-alkanes. In LAB produced by the Detal™ solid catalyst alkylation process approximately 25–35 wt-% of the n-phenyl-alkanes are 2-phenyl-alkanes. In LAB produced using mordenite catalyst, about 70–80 wt-% of n-phenyl-alkanes are 2-phenyl-alkanes. It is known to produce LAB using both a high-fluorine mordenite-containing catalyst and a silica-alumina catalyst.
The dehydrogenation of linear paraffins to produce linear olefins typically produces aromatic byproducts, as described in U.S. Pat. No. 5,276,231. These aromatics are of the same carbon number as the paraffin being dehydrogenated and may be viewed as aromatized normal paraffins. Typically, the concentration of these aromatic byproducts in the monoolefinic stream is 3–4 wt-%. U.S. Pat. No. 5,276,231 discloses processes for removing these aromatic byproducts.
Processes are sought that produce LAB having practically a range of 2-phenyl-alkane contents.